Laura and I are going to be doing a presentation on low oxygen levels at high altitudes and I thought I would share some of the information.
There are 3 Beasts of Burden on Mt. Everest.
1. JOKYO The Jokyo, also called Dzopko or Zuikos, is a yak/cow cross and carries supplies below 3500m. On our trip we saw lots of them below Namche Bazar. They are used instead of yaks at lower levels because yaks have thick skin with few functioning sweat glands and lots of hair; therefore, they overheat at lower hotter altitudes.
2. YAK The yak carries supplies above 3500m up to Base Camp at 5300m. At Base Camp there is 1/2 the amount of oxygen that there is at sea level. They are truly amazing animals with special phyiological adaptations. They have a large chest cavity which permits the development of large lungs and a large heart. Their trachea is longer and more flexible which allows the yak to adjust quickly to oxygen demands allowing them to breathe rapidly if necessary. It is believed that yaks' red blood cells have a greater ability for oxygen absorption but scientists are unsure why. Some believe they have larger red blood cells; thus, more hemoglobin for the oxygen to attach to. Others believe that their hemoglobin composition has a greater affinity to oxygen. Still others believe that when the animal is stressed its spleen releases large quantites of red blood cells. Male yaks have been known to survive as high as 7200m.
3. HUMAN PORTERS - both male and female. Porters are not Sherpas. Porters come from the low valleys and in the caste system that exists in Nepal they are considered at the bottom. They are very very poor and all that I met were illiterate. They have an extremely hard life. Other than when they pick up your bags in the morning and drop them off at the next teahouse you have very little contact with them. (My porter Dawa was the exception since he was told to stick to me like glue.) The government, better outfitters, and compassionate trekkers and climbers are trying very hard to ensure that porters are treated more fairly.